A lithium-ion battery is an electrochemical generator which is capable of transforming stored chemical energy into electric energy by reversible exchange of lithium ions. A lithium-ion battery is conventionally formed of two electrodes having an electrolyte forming an electrochemical core arranged therebetween.
FIG. 1 illustrates a lithium-ion battery of the state of the art formed of a single electrochemical core. The electrochemical core is formed by a positive electrode 10, a negative electrode 11, and an electrolyte 12 separating the two electrodes 10-11. Preferably, positive electrode 10 is made of lithium cation insertion materials, such as cobalt dioxide or manganese. Negative electrode 11 is most often made of graphite carbon, of titanate, of metal lithium, or of silicon. Electrolyte 12 is formed of a polymer separator or microporous composite impregnated with electrolyte or catholyte allowing the migration of the lithium ion from positive electrode 10 to negative electrode 11 and conversely, thus generating the current between the two electrodes 10, 11.
The access to positive electrode 10 is provided by a first current collector 13 preferably made of aluminum. The access to negative electrode 11 is provided by a second current collector 14. Second current collector 14 is conventionally made of copper for a graphite carbon electrode 11, of aluminum for a titanate or stainless steel or nickel electrode 11 according to the battery type.
Eventually, layers 10-14 are integrated in a package 15 so that only a portion of collectors 13, 14 is accessible outside of package 15. Package 15 may be rigid or flexible and guarantees the tightness of the electrochemical core with respect to polluting outside elements such as water, oxygen, and nitrogen. Package 15 may be made in the form of a thermoformable pouch or a hard container made of stainless steel or of aluminum.
The lithium-ion battery of FIG. 1 is made in planar form by planar layers. As a variation, a lithium-ion battery may also be made in cylindrical form by concentric layers. The electrochemical core may also be made in spiral or prismatic form. Further, certain batteries are formed of a plurality of stacked electrochemical cores.
The new generation of batteries comprises positive electrodes formed by carbon fabrics or carbon felts. Indeed, carbon felt is a material enabling to efficiently insert the products of the electrochemical reaction into the pores of the carbon felt. However, since carbon felt is not a metallic element, the binding of the metal collector to the positive electrode cannot be performed by a conventional welding.
Document KR 2012 0029289 provides holding the carbon felt in a metal frame having the collector welded thereto. However, the frame increases the battery bulk and the method of holding the carbon felt on the frame is complex.
The aim of the invention is to simplify the bonding and the electric contact between a carbon felt and a metal collector of a battery.